There are many kinds of touch panel devices (in the following, it is called as touch panel in short), which are resistive, capacitive, optical touch panels, etc. A resistive touch panel is formed by overlapping an upper and a lower conductive layer. The pressure applied to the touch panel will cause the upper layer electrode and the lower layer electrode to conduct. A controller calculates the positions of touch points by detecting the voltage variations of the touch panel. As to the capacitive touch panel, a capacitive symptom will occur between the electrodes built in the panel and the static electricity carried by human body. Using time delays caused by charging and discharging a capacitor, the coordinates of the touch points can be obtained. Optical touch panels adopt light source obstruction principle. The composition of light sources and receivers are formed as a matrix on a surface of the optical touch panel. The position of the touch point can be detected once the light source was obstructed.
So far, up to year 2010, the resistive touch panels occupied a very big market share. The capacitive touch panels are not so popular because there are so many problems waiting to be solved. Mainly the capacitive touch panel utilizes the capacitive interaction of finger touch to judge the position by detecting the capacitive variations. But the size of touching area, the temperature, the humidity and the pressure will influence the capacitive volume. The noise of signals induced by finger touch causes the treatment of signals to become difficult. This causes that the costs go higher and become less popular. Therefore, to make the capacitive touch panel more popular, it is necessary to find ways to solve these existing problems.